BKDR_VAWTRAK.GS


 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

422,912 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

06 Dec 2014

Arrival Details

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This backdoor creates the following folders:

  • %User Temp%\EicazAczax

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
GavdIfki = "regsvr32.exe %User Profile%\GavdIfki\GavdIfki.dat "

Other System Modifications

This backdoor deletes the following folders:

  • *t

It adds the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\Classes\
CLSID\{117A5899-70DC-4EA0-B35F-15F35AEF383F}

HKEY_CURRENT_USER\SOFTWARE\Classes\
CLSID\{6DC27B69-71ED-4D68-A596-26246E600862}

It adds the following registry entries:

HKEY_CURRENT_USER\CLSID\{117A5899-70DC-4EA0-B35F-15F35AEF383F}
#sd = "{random values}"

HKEY_CURRENT_USER\Software\Classes\
CLSID\{6DC27B69-71ED-4D68-A596-26246E600862}
{70F02777-377A-401E-81D9-18A6337C4BAD} = "{random values}"

HKEY_CURRENT_USER\CLSID\{6DC27B69-71ED-4D68-A596-26246E600862}
{70F02777-377A-401E-81D9-18A6337C4BAD} = "{random values}"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
NoProtectedModeBanner = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
TabProcGrowth = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
Zones\3
2500 = "3"

HKEY_CURRENT_USER\CLSID\{117A5899-70DC-4EA0-B35F-15F35AEF383F}
#cert = "{random values}"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\Safer\
CodeIdentifiers
DefaultLevel = "4"

(Note: The default value data of the said registry entry is 40000.)

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\Safer\
CodeIdentifiers
TransparentEnabled = "1"

(Note: The default value data of the said registry entry is 1.)

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\Safer\
CodeIdentifiers
PolicyScope = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\Safer\
CodeIdentifiers
ExecutableTypes = "WSC"

(Note: The default value data of the said registry entry is {random values}.)

Dropping Routine

This backdoor drops the following files:

  • %User Temp%\EicazAczax\GavdIfki.dat

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Other Details

This backdoor deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.700

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Restart in Safe Mode

[ Learn More ]

Step 3

Delete this registry key

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\SOFTWARE\Classes\CLSID
    • {117A5899-70DC-4EA0-B35F-15F35AEF383F}
  • In HKEY_CURRENT_USER\SOFTWARE\Classes\CLSID
    • {6DC27B69-71ED-4D68-A596-26246E600862}

Step 4

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • GavdIfki = "regsvr32.exe %User Profile%\GavdIfki\GavdIfki.dat "
  • In HKEY_CURRENT_USER\CLSID\{117A5899-70DC-4EA0-B35F-15F35AEF383F}
    • #sd = "{random values}"
  • In HKEY_CURRENT_USER\Software\Classes\CLSID\{6DC27B69-71ED-4D68-A596-26246E600862}
    • {70F02777-377A-401E-81D9-18A6337C4BAD} = "{random values}"
  • In HKEY_CURRENT_USER\CLSID\{6DC27B69-71ED-4D68-A596-26246E600862}
    • {70F02777-377A-401E-81D9-18A6337C4BAD} = "{random values}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • NoProtectedModeBanner = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • TabProcGrowth = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3
    • 2500 = "3"
  • In HKEY_CURRENT_USER\CLSID\{117A5899-70DC-4EA0-B35F-15F35AEF383F}
    • #cert = "{random values}"

Step 5

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Safer\CodeIdentifiers
    • From: DefaultLevel = "4"
      To: DefaultLevel = ""40000""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Safer\CodeIdentifiers
    • From: TransparentEnabled = "1"
      To: TransparentEnabled = ""1""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Safer\CodeIdentifiers
    • PolicyScope = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Safer\CodeIdentifiers
    • From: ExecutableTypes = "WSC"
      To: ExecutableTypes = ""{random values}""

Step 6

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Temp%\EicazAczax\GavdIfki.dat

Step 7

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Temp%\EicazAczax

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_VAWTRAK.GS. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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